1. Field of the Invention
The present invention relates to an orthogonal transform apparatus and method capable of enlarging and shrinking an image and orthogonally transforming input data in orthogonal transform of an image such as dynamic-image data.
2. Related Art of the Invention
The method disclosed in the official gazette of Japanese Patent Laid-Open No. 143723/1993 has been known so far as a method for shrinking a dynamic image. Moreover, the method disclosed in the official gazette of Japanese Patent Application No. 200362/1992 has been known so far as a method for enlarging a dynamic image. The enlarging and shrinking methods disclosed in these official gazettes purpose the input of an 8-row 8-column discrete cosine transform (DCT) coefficient.
FIG. 9 shows a conventional inverse-DCT apparatus for shrinking an image size. In FIG. 9, a changeover switch 95 has input terminals a, b, and c. The input terminal. is connected to the output of an 8.times.8 inverse-DCT circuit 92, the input terminal b is connected to that of 4.times.4 inverse-DCT circuit 93, and the input terminal c is connected to that of a 2.times.2 inverse-DCT circuit 94. Any one of these input terminals is selected and set in accordance with a control signal supplied from a control circuit 97 to output pixel data 98. The 8.times.8 inverse-DCT circuit 92 is a circuit for inverse-DCT-processing an 8.times.8 DCT coefficient 91. The 4.times.4 inverse-DCT circuit 93 is a circuit for inverse-DCT-processing a 4.times.4 DCT coefficient to reduce the length and width of an image size to 1/2 respectively and the 2.times.2 inverse-DCT circuit 94 is a circuit for inverse-DCT-processing a 2.times.2 DCT coefficient and reducing an image size to 1/4. In this case, when an input is the 8.times.8 DCT coefficient 91, the 8.times.8 DCT coefficient 91 is directly input to the 8.times.8 inverse-DCT circuit 92 and inverse-DCT-processed to become 8.times.8 pixel data. To shrink an image to 1/2, the 4.times.4 DCT coefficient of the low-band component of the 8.times.8 DCT coefficient 91 is input to the 4.times.4 inverse-DCT circuit 93 and inverse-DCT-processed to become 4.times.4 pixel data and a 1/2-size image. To shrink an image to 1/4, the 2.times.2 DCT coefficient of the low-band component of the 8.times.8 DCT coefficient 91 is input to the 2.times.2 inverse-DCT circuit 94 and inverse-DCT-processed to become 2.times.2 pixel data and a 1/4-size image.
FIG. 10 shows a conventional inverse-DCT apparatus for enlarging an image size. In FIG. 10, enlargement-block generation means 102 generates a new DCT coefficient of N1.times.N2 size (N1 and N2 are integers larger than 8) by using the 8.times.8 DCT coefficient 101 as a low-band component and a high-band component as 0. By inverse-DCT-processing the new N1.times.N2 DCT coefficient by inverse-DCT means 103, N1.times.N2 pixel data 104 is generated and an image enlarged by N1/8 times in the longitudinal direction and by N2/8 times in the cross direction.
To realize the orthogonal transform apparatus capable of enlarging and shrinking an image with hardware, a inverse-DCT circuit for enlargement and a inverse-DCT circuit for shrinkion are necessary and moreover, an n-order inverse-DCT circuit (n is a natural number) is necessary. Thereby, because n inverse-DCT circuits are necessary, it is necessary to newly design an n-order inverse-DCT circuit for each degree. Moreover, a problem occurs that a circuit size increases because n inverse-DCT circuits are combined.